France's third weekend in the streets
About 320,000 people marched across France on Oct. 31 in a youth-led movement over living costs and public services, some of them in Halloween costume. Most marches were peaceful, but police clashed with masked rioters as crowds dispersed. Read at The Guardian →
The Nika riots
What happened then
Anger in the Hippodrome turned into a week of rioting that burned much of Constantinople, the old Hagia Sophia included, and crowds proclaimed a rival emperor, Hypatius.
What caused it
There was resentment over heavy taxes and harsh officials such as John the Cappadocian. The spark came when a botched execution of rioters from both of the big chariot-racing factions, the Blues and the Greens, united the two against the emperor.
How it was resolved
Justinian sacked unpopular ministers, but the riots went on. According to Procopius, Theodora talked him out of fleeing. The generals Belisarius and Mundus then trapped the crowd in the Hippodrome, and Procopius reports some 30,000 killed.
How it turned out
Justinian's hold on power was never stronger. He rebuilt the Hagia Sophia, which was dedicated in 537 and still stands. The cost was a city that remembered how the protest ended.
Sources: Procopius, History of the Wars I (Project Gutenberg) · Wikipedia: Nika riots · Britannica: Hagia Sophia
Further reading: Justinian: Emperor, Soldier, Saint by Peter Sarris